将字符串转换为浮点会产生意外的收益。 爪哇

Question

I have a 2d array which was created by parsing data in a file. The method sends each part of data to a string. I am trying to convert the array from strings to floating point. Everything prints alright except for one column.

For example:

2015/10/21,113.7600,42276880.0000,114.0000,115.5800,113.7000

2015/10/20,113.7700,48929200.0000,111.3400,114.1700,110.8200

2015/10/19,111.7300,29723750.0000,110.8000,111.7500,110.1100

Converts to:

0.0 113.76 4.227688E7 114.0 115.58 113.7 

0.0 113.77 4.89292E7 111.34 114.17 110.82

0.0 111.73 2.972375E7 110.8 111.75 110.11 

The date column is meant to return 0.0 but the 3rd column returns a weird response. Is this an error with my code or the data?

Converting string array to floating point array method

public void createDataArray(String [] [] n){
    for(int x=0;x<n.length;x++) {
        for(int y=0;y<n [x].length;y++) {
            switch(y) {
            case 0:
                dataArray[x] [y] = 0;
                break;
            case 1:
                dataArray[x] [y] = new Float(n[x] [y]);
                break;
            case 2:
                dataArray[x] [y] = new Float(n[x] [y]);
                break;
            case 3:
                dataArray[x] [y] = new Float(n[x] [y]);
                break;
            case 4:
                dataArray[x] [y] = new Float(n[x] [y]);
                break;
            case 5:
                dataArray[x] [y] = new Float(n[x] [y]);
                break;
            case 6:
                dataArray[x] [y] = new Float(n[x] [y]);
                break;
            }
        }
    }
}

New array printing method

public void printArray() {
    for(int x=0;x<dataArray.length;x++) {
        for(int y=0;y<dataArray[x].length;y++) {
            System.out.printf("%s ", dataArray[x] [y]);
        }
        System.out.println();
    }
}

If you would like any more information just ask. I'm fairly certain its something wrong with the data but even after giving it fake values it still returns a similar response.

Answer 1

That's scientific notation, try using %f for the floats instead of %s (string). You can get more control as necessary: https://docs.oracle.com/javase/tutorial/java/data/numberformat.html

Answer 2

Based on your requirements, you have to use %f for printing float/double.

Example:

String[] floatNumbers = {"42276880.0000", "48929200.0000","29723750.0000"};

for (String s: floatNumbers ) {
    Float temp = new Float(s);
    System.out.printf("%f\t", temp);
    System.out.println(temp);
}

Output:

42276880.000000 4.227688E7

48929200.000000 4.89292E7

29723750.000000 2.972375E7

Docs